Analysis of Medication Use Patterns: Apparent Overuse of Antibiotics and Underuse of Prescription Drugs for Asthma, Depression, and CHF

OBJECTIVES: To assess the appropriateness of prescription medication use based upon widely accepted treatment guidelines. METHODS: We analyzed administrative claims for the period October 1, 1998, through September 20, 1999, supplied by 3 California health plans to determine medication use patterns for outpatient prescriptions. We compared these patterns to those expected in the presence of adherence to treatment guidelines. RESULTS: During the study period, only 27.5% of antidepressant users received the recommended 6 months of continuous therapy, only 49.0% of diagnosed asthma patients received at least one inhaled corticosteroid prescription (compared to 67.1% who received at least one inhaled beta-agonist prescription), and only 54.5% of patients diagnosed with congestive heart failure (CHF) received an angiotensin-converting enzyme (ACE) inhibitor. Of patients who had a diagnosis of common cold or upper respiratory tract infection, 35.7% received antibiotics. CONCLUSIONS: There is a remarkable degree of apparent overuse and underuse of prescription medications despite the existence of clinical guidelines to support appropriate use in the conditions studied. Effective medications appear to be underused for patients with asthma, CHF, and depression. Antibiotics appear to be overused for the common cold and upper respiratory infections. More effective efforts must be made to address appropriate use of medications. Without these efforts, improved quality of care and decreased total health system costs are unlikely to be realized.

n the 12-month period from September 2000 through August 2001, the sales of prescription drugs through retail pharmacies in the United States increased 16% over the previous 12 months. 1 Although this magnitude of increase is similar to those seen annually between 1987 and 1994 and between 1994 and 1999, 2 the mix of factors driving this persistent rise has changed.
Prior to 1994, approximately one half of this total annual increase was due to price increases for existing drugs. Subsequent to 1994, only 20% of the annual increase in spending was attributable to price increases of existing products. Instead, about 80% of the increase in drug spending in the period 1994 to 1999 was due to increases in spending on new products and changes in the volume and mix of prescription pharmaceuticals. 2 Other researchers recently estimated that retail spending increases between 2000 and 2001 was 37% attributable to price increases, 24% to a shift to higher-cost drugs, and 39% to an increase in the number of prescriptions. 3 The underlying causes of the increases in drug utilization differ depending on the specific drug class and indications for use. 3a Specifically, the influence of price factors (inflation rate, mix of established versus new therapies, and new drug prices) and volume factors (prevalence, prescriptions, and days per prescription for established drugs versus new therapies) vary for different drug classes. The major question for health care professionals and health policy groups is obvious: "How appropriate is this increased drug utilization?" Geographic variation in care has been used in the health services literature as a potential indicator of quality of care for surgical and diagnostic procedures. [4][5][6][7] Relatively little is known either about the influence of geography on outpatient medication use or the appropriateness of this use. Recently, significant geographic variation for certain drug classes has been observed. 7a We examined the geographic variability of outpatient medication use in a number of common conditions in 11 California regions and in a managed care population outside of California and found surprisingly few differences among geographic regions. 8 In either case, an important question is whether the medication utilization rate observed is "right," or reflects a uniform need for improvement in medication use across a broad population.
We undertook an analysis to assess the magnitude of opportunity to improve medication use; i.e., are medication usage patterns "right"? This report will focus on the patterns of drug use that we observed within the same sample of California patients to assess the appropriateness of the current levels of drug utilization. For this part of the study, we selected medical conditions for which well-documented evidence and widely accepted treatment guidelines provide clear recommendations for appropriate drug therapy. The medications and conditions studied also represent 2 different types of medication quality concerns: underuse (inhaled corticosteroid [ICS] use in asthma, angiotensin-converting enzyme [ACE] inhibitor or angiotensin II receptor antagonist [ARB] use in congestive heart failure [CHF], and duration of antidepressant therapy for depression) and overuse (antibiotic use in the common cold and upper respiratory tract infection).

■■ Methods Data Sources
This study employed administrative claims data from 3 of the 10 largest health plans in California. Members were selected from large group plans to eliminate any biases inherent in benefit coverage and underwriting differences for small groups and individual coverage. Each plan submitted claims for a sample of 165,000 to 257,000 randomly selected members who had continuous medical and pharmacy coverage for the 18-month period from April 1, 1998, through September 30, 1999. These data were aggregated to form the California study population.

Study Population
The aggregated California health plan population for this study included a total of 552,748 patients (i.e., members who had benefit coverage and received services during the study period) ( Table 1). The average age for this population was 47.4 years with slightly more females than males (54.6% versus 45.4%) and was considerably older than the U.S. population in 1999, which had an average age of 36.4 years. 9 The distribution of health plan type for this study population was: health maintenance organization (HMO), 42.3%; preferred provider organization (PPO), 56.6%; point of service (POS), 1.0%; and other, 0%.

Analytic Approach
This study provides a descriptive analysis of markers of overuse and underuse of outpatient medications in 4 common therapeutic areas. Therapeutic areas for study were chosen to represent common diseases for which the available evidence can support an assessment of the clinical appropriateness of current treatment patterns. Tables 2 and 3 describe the rationale for inclusion of each of the selected therapeutic areas, the marker used to assess appropriateness, and the method used to identify patients for inclusion within each therapeutic area. The study evaluated prescription dispensing patterns for the 12-month period of October 1, 1998, through September 30, 1999.

■■ Results
See Table 4 for a summary of study results.
Asthma. The number of patients with a diagnosis of asthma was 18,693 (3.4% of the study population). Table 5 provides an overview of the observed usage of ICSs, which guidelines recommend be used on a chronic basis as the foundation of therapy with other drugs that are commonly used in asthma but that do not treat the underlying cause of the disease. Congestive heart failure. The number of patients with the diagnosis of congestive heart failure was 9,648 (1.7% of the study population). Of these patients, the percentage filling at least one prescription during the study period was 54.4% for ACE inhibitors, 8.4% for ARBs, and 1.8% for ACE combinations. The percentage of CHF patients who filled at least one prescription for any ACE inhibitor or ARB was 61.1%, and the average number of prescriptions filled per patient during the study period was 6.7.

Study Population Characteristics
Antidepressant use. The number of patients who filled at least one prescription for an antidepressant during the study period was 19,766 (3.6% of the study population), of which only a surprisingly low 27.7% received a minimum of 6 months of continuous therapy during the study period. In comparison, 59.0% of these patients received therapy for less than 3 months and 13.3% received continuous therapy for 3 to 6 months. The average number of prescriptions filled per antidepressant user was 3 during the 12-month study period.
Common cold/upper respiratory tract infections. The number of patients with any diagnosis of respiratory tract infection was 158,553, of which 33,285 (21.0%, or 6.0% of the entire study population) had a diagnosis of either the common cold or upper respiratory tract infection (URTI). Of those patients with the diagnosis of common cold or URTI, 35.7% filled at least one prescription for antibiotics. In comparison, the use of antibiotics for the other respiratory tract infections assessed ranged from 51.3% for the group of diagnoses pharyngitis/tonsillitis/laryngitis/tracheitis to 62.6% for the diagnosis sinusitis.

■■ Discussion
This study attempts to assess real-life patterns of drug treatment against the yardstick of guidelines and clinical evidence in order to evaluate appropriateness of therapy. The results of this study suggest that a remarkable degree of overuse and underuse of prescription medications continued to exist at the time of the study despite the existence of clinical guidelines to support appropriate use in the conditions studied. Only 50% of patients with asthma received ICSs, drugs that are known to treat the underlying cause of asthma and improve mortality and morbidity; at the same time, more than three quarters of the asthma patients took at least one form of beta agonist, a class of drugs that treats the symptoms but not the underlying cause of the disease While an administrative claims analysis cannot discern patients with persistent asthma who are candidates for ICS therapy from those with mild intermittent disease, our patient identification criteria sought patients who had significant disease (hospitalization or emergency room visit) or multiple encounters for their asthma; i.e., individuals who presumably had symptoms significant enough to actively seek health care for their asthma. Even accounting for avoidance of ICS in young children due to concerns regarding the potential impact on growth, a substantial proportion of asthmatics do not receive an important medication for their disease.
Although ACE inhibitors and angiotensin II blockers were used in 60% of patients with CHF, the very significant impact of these medications on morbidity and mortality 25 in this condition and the wide coverage of their benefits in the medical media should have resulted in their use in a much larger percentage of patients, considering that our patient population had either hospitalizations or multiple encounters for their CHF. Slightly more than 25% of antidepressant users took antidepressants continuously for an adequate time period to prevent relapse of their disease, with the majority of patients taking these medications for less than 3 months. While some patients could have been receiving antidepressants for a nondepression indication, we still would have expected a higher rate of longerterm use. Finally, antibiotics were used in just more than one third of patients with conditions that are most likely of viral origin (e.g., the common cold and upper respiratory tract infections) and for which antibiotic treatment is not indicated, thereby increasing the avoidable risk of antibiotic resistance.
These results are particularly surprising and disturbing when we take into account the fact that 3 of the conditions studied (asthma, CHF, and depression) are known to produce high costs to the health care system. As such, they have been the subject of extensive managed care scrutiny with programs in disease management, patient education and compliance, and drug utilization review and continuing medical education for both primary care physicians and specialists. Our previous report 8 demonstrated that there was little geographic variability in the use of these medications. Although reducing variability

Condition Definition
has always been an important goal of quality assurance programs, these findings suggest that despite greater uniformity of practice patterns, there appears to be a need for ongoing improvement in the appropriateness of use of medications in the therapeutic areas studied. We acknowledge the limitations inherent in the use of administrative claims as a data source for this study. Administrative claims data cannot provide clinical-record level detail (e.g., severity of disease, therapy contraindications) that would be needed to assess true appropriateness of care for specific patients. However, patient identification algorithms in this study were consistent with existing definitions for external quality assessment approaches such as those used by the National Committee on Quality Assurance. Our study was designed as an initial descriptive analysis to identify the magnitude of potential under-or over-utilization of commonly used medications across a large population of managed care patients but did not attempt to utilize more complex methodologies to assess the appropriateness of drug use at an individual patient level.

■■ Conclusion
Patients are continuing to underuse and overuse important drug therapies in 4 common therapeutic areas. The underlying causes of these problems remain uncertain. Contributing factors could include prescribing practices, poor patient compliance, excessive patient demand, and inconsistent or inadequate monitoring of drug therapy use. Further study to identify the importance of these factors and predictors of potentially inappropriate utilization is needed.
What is clear is that despite the efforts of the health care system, traditional quality improvement programs continue to leave many more opportunities for optimizing care. More effective efforts must be made to address both the underuse and overuse of specific therapies. These efforts must include both studies to understand the best methods to more successfully reinforce appropriate use of medications according to accepted guidelines and innovative tools to support physician decision making and patient compliance. Without these focused efforts, it is unlikely that the opportunities of improved quality of care and decreased total health system costs through the appropriate use of pharmaceutical products can be fulfilled.

ACKNOWLEDGMENTS
The authors thank Sandra Aronberg, Jeff Kamil, Nancy Stalker, and Cheryl Tanigawa for assisting them with obtaining data and for their contributions to the Advisory Board; Robert W. Dubois and Elaine Batchlor for their contributions in designing the geographic variations study; Mary Patton and Robert Fowler for their analytic expertise; and Merle Haberman and Dorothy George for their review of and contribution to this paper.

DISCLOSURES
Funding for this research was provided by a grant from the California HealthCare Foundation. Protocare Sciences is a health care consulting company that was commissioned by the California HealthCare Foundation to design  the study and analyze and interpret the data. Authors Karen Gilberg and Sharon Isonaka are employed by Protocare Sciences, and author Marianne Laouri is employed by the California HealthCare Foundation. Gilberg served as principal author of the study. Study concept and design were contributed by Laouri and author Sally Wade, and analysis and interpretation of data were contributed by Gilberg, Laouri, Wade, and Isonaka. Drafting of the manuscript was primarily the work of Gilberg and Wade and its critical revision was the work of Laouri and Isonaka. Statistical expertise was contributed by Gilberg.